1. Field of the Invention
The present invention relates to a light irradiation annealing apparatus called a Ramp annealing apparatus or a rapid thermal annealing (RTA) apparatus for annealing semiconductor wafers.
2. Description of the Related Art
Generally, in a prior art Ramp annealing apparatus, an annealing chamber is in a vacuum state, so that semiconductor wafers are heated only by radiation of a lamp heater. This will be explained later in detail.
In the above-described prior art Ramp annealing apparatus, however, since the temperature of the semiconductor wafer depends upon the resistivity, if the temperature of the semiconductor wafer is controlled by the power of the lamp heater, the power condition of the apparatus has to be adjusted to conform with the resistivity of the semiconductor wafer, which would increase the manufacturing cost.
Note that, if the temperature of the semiconductor wafer is monitored by a pyrometer or a thermocouple, the power of the lamp heater can be controlled based on the monitored temperature.